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A Global Look at Moving Air: Atmospheric Circulation

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A Global Look at Moving Air: Atmospheric Circulation

Air in the atmosphere moves around the world in a pattern called global atmospheric circulation. Credit: UCAR

Even with disruptions like
weather fronts and storms, there is a consistent pattern to how air moves
around our planet’s atmosphere. This pattern, called atmospheric circulation,
is caused because the Sun heats the Earth more at the equator than at the poles. It's also affected by the spin of the Earth.

In the tropics, near the
equator, warm air rises. When it gets about 10-15 km (6-9 miles) above the Earth
surface it starts to flow away from the equator and towards the poles. Air that
rose just north of the equator flows north. Air that rose just south of the
equator flows south. When the air cools, it drops back to the ground, flows
back towards the Equator, and warm again. The, now, warmed air rises again, and
the pattern repeats. This pattern, known as convection, happens on a global scale. It also happens on a small
scale within individual storms.

But because
Earth is spinning, the air that moves north and south from the equator also
turns with the spin of the Earth. Air going north turns to the right. Air
traveling south turns to the left. The power of Earth’s spin to turn
flowing air is known as the Coriolis Effect. If the Earth didn’t spin, there
would be just one large convection cell between the equator and the North Pole
and one large convection cell between the equator and the South Pole. But because the Earth does spin,
convection is divided into three cells north of the equator and three south of
the equator.